Obesity is a condition characterized by an increase in body fat content resulting in excess body weight above accepted norms. Obesity is the most important nutritional disorder in the western world and represents a major health problem in all industrialized countries. This disorder leads to increased mortality due to increased incidences of diseases such as cardiovascular disease, digestive disease, respiratory disease, cancer and type 2 diabetes. Searching for compounds that reduce body weight has been going on for many decades. One line of research has been activation of serotoninergic systems, either by direct activation of serotonin receptor subtypes or by inhibiting serotonin reuptake. The exact receptor subtype profile required is however not known.
Serotonin (5-hydroxytryptamine or 5-HT), a key transmitter of the peripheral and central nervous system, modulates a wide range of physiological and pathological functions, including anxiety, sleep regulation, aggression, feeding and depression. Multiple serotonin receptor subtypes have been identified and cloned. One of these, the 5-HT6 receptor, was cloned by several groups in 1993 (Ruat, M. et al. (1993) Biochem. Biophys. Res. Commun. 193: 268-276; Sebben, M. et al. (1994) NeuroReport 5: 2553-2557). This receptor is positively coupled to adenylyl cyclase and displays affinity for antidepressants such as clozapine. Recently, the effect of 5-HT6 antagonist and 5-HT6 antisense oligonucleotides to reduce food intake in rats has been reported (Bentley, J. C. et al. (1999) Br J Pharmacol. Suppl. 126, P66; Bentley, J. C. et al. (1997) J. Psychopharmacol. Suppl. A64, 255; Woolley M. L. et al. (2001) Neuropharmacology 41: 210-219).
Compounds with enhanced affinity and selectivity for the 5-HT6 receptor have been identified, e.g. in WO 00/34242 and by Isaac, M. et al. (2000) 6-Bicyclopiperazinyl-1-arylsulphonylindoles and 6-Bicyclopiperidinyl-1-arylsulphonylindoles derivatives as novel, potent and selective 5-HT6 receptor antagonists. Bioorganic & Medicinal Chemistry Letters 10: 1719-1721 (2000), Bioorganic & Medicinal Chemistry Letters 13: 3355-3359 (2003), Expert Opinion Therapeutic Patents 12(4) 513-527 (2002).